Make sure that LW's not still running...open Task Manager & if there's a LW process running, end the process.
Try the advice here for how to uninstall/reinstall:
http://www.gnutellaforums.com/320995-post377.html
If you're still having connection problems after reinstalling, try the fixes in this thread:
If LW Will Not Connect
If nothing there helps, post back with your system details.